At present, AC speed regulating system with flux-weakening control strategy and high speed control performance has been widely used in the fields of spindle drive of numerical control machine tools and electric vehicles.
After the motor speed exceeds the base speed, since the output voltage of inverter reaches its maximum value, it is usually to reduce the magnetic flux in the induction motor, i.e. to reduce the back electromotive force by using flux-weakening controlling method, so as to meet required back electromotive force of rotor for increasing the motor speed. The traditional flux-weakening controlling method is to make the excitation of the rotor inversely proportional to the speed. However, the above controlling method can't provide the maximum output torque, seriously affecting the motor performance.
In the flux-weakening region of V/f controlled induction motor, a smaller stator frequency acceleration value cannot provide sufficient torque for speeding up the motor, so that the acceleration process of the rotor of the motor becomes longer. However, a larger stator frequency acceleration value can lead to overcurrent shutdown and system collapse. In addition, the leakage inductance parameter has a significant impact on the system stability when the motor speed exceeds the base speed. If the leakage inductance parameter is underestimated, there will be no stable operation point in the induction motor.